/Engine/Plugins/Interchange/Runtime/Source/Import/Public/MaterialX/MaterialXUtils/MaterialXSurfaceShaderAbstract.h
Return the innermost file prefix of an element in the current scope, if it has none, it will take the one from its parents
a file prefix or an empty string
[FString](API\Runtime\Core\Containers\FString) GetFilePrefix ( MaterialX::ElementPtr Element ) const